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Radiation Damage and Racemic Protein Crystallography Reveal the Unique Structure of the GASA/Snakin Protein Superfamily
Author(s) -
Yeung Ho,
Squire Christopher J.,
Yosaatmadja Yuliana,
Panjikar Santosh,
López Gemma,
Molina Antonio,
Baker Edward N.,
Harris Paul W. R.,
Brimble Margaret A.
Publication year - 2016
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201602719
Subject(s) - residue (chemistry) , protein crystallization , chemistry , crystal structure , crystallization , protein structure , stereochemistry , crystallography , biochemistry , organic chemistry
Proteins from the GASA/snakin superfamily are common in plant proteomes and have diverse functions, including hormonal crosstalk, development, and defense. One 63‐residue member of this family, snakin‐1, an antimicrobial protein from potatoes, has previously been chemically synthesized in a fully active form. Herein the 1.5 Å structure of snakin‐1, determined by a novel combination of racemic protein crystallization and radiation‐damage‐induced phasing (RIP), is reported. Racemic crystals of snakin‐1 and quasi‐racemic crystals incorporating an unnatural 4‐iodophenylalanine residue were prepared from chemically synthesized d ‐ and l ‐proteins. Breakage of the C−I bonds in the quasi‐racemic crystals facilitated structure determination by RIP. The crystal structure reveals a unique protein fold with six disulfide crosslinks, presenting a distinct electrostatic surface that may target the protein to microbial cell surfaces.